1. Field of the Invention
The present invention relates to an incising device for incising or cutting out the valves of a vein.
2. Description of the Related Art
If an artery is clogged due to atheroma formed at a branch blood vessel, the surgical operation is carried out to provide a bypass for the closed portion of the artery by utilizing a saphenous vein. Since a vein has valves for causing the blood to flow in one direction only, the valves have to be cut out before using the vein as a bypass.
The surgical operation for cutting out the venous valves is carried out as follows. First two openings are formed at positions which are upstream and downstream of that portion of the vein from which the valves are to be cut out. At this time, the vein is clamped in the neighborhood of the two openings, so as to stop the blood flow. The incising device is inserted from the upstream opening, and is then pulled back for the incision of the valves after it is introduced up to a predetermined point. Since the incising device has a cutting edge directed backward, the valves are incised or cut out when the incising device is pulled back.
A typical example of a conventional venous valve-incising device of this type is disclosed in Published Unexamined Japanese Utility Model Application No. 63-38505. In the device disclosed in this reference, a guide tube and cutting blades are coupled to the tip end of a flexible sheath. The device permits the number of cutting blades to be changed in accordance with the incision area, but does not allow the use of suitable cutting blades in accordance with the size of the vein or the state of the venous valves.
In the surgical operation for cutting out the venous valves, the operator can visually confirm the shape and other features of the venous valves by inserting a fiber scope into the vein beforehand. Therefore, the operator can select a cutting edge having the most suitable shape for the treatment, before he or she actually inserts the incising device into the vein. However, once the incising device is inserted in the vein, the operator is not allowed to replace the cutting edge with another. Therefore, if the replacement of the cutting edge is absolutely necessary, the operator has to pull the incising device out of the vein through the upstream opening, replace the cutting edge with another, and insert the incising device again into the vein. When the incising device is pulled, the cutting edge may incise the valves in an undesirable manner. In some cases, the cutting edge may catch on a side branch and tear it.